The fabrication of semiconductor devices requires extensive chemical processing of the surface and body of a silicon wafer. Such processing typically involves chemical reactions such as, for example, diffusion, oxidation and deposition. For processes involving deposition, dielectric materials such as polycrystalline silicon, silicon nitride and silicon dioxide are deposited through suitable chemical means on the surface of the wafer. In deposition applications, species from a source such as a target, a gas inlet manifold and the like may deposit on exposed internal chamber surfaces, including the chamber walls and hardware. Deposition rings are designed to intercept such stray species. Over an extended use, the deposition ring degrades and must be regularly replaced to ensure optimal performance of the deposition equipment.
The deposition ring is generally composed of a ceramic substrate coated with a metallic layer. The metallic layer provides a surface on which the stray species may be readily deposited. The metallic layer is generally composed of a metal that has limited reactivity with the ceramic substrate, resists corrosion and adheres well to the substrate and is economically competitive. Aluminum is the metal that closely matches these requirements. The aluminum layer is generally arc sprayed onto the ceramic substrate and enhances the adhesion of tantalum deposition, for example, or other depositions, thereby improving the performance of the deposition ring. The metal-based top layer is generally composed of tantalum as a deposition species that is deposited through vacuum deposition during use of the deposition ring in semiconductor manufacturing.
Sustained exposure of the ceramic deposition ring to the deposition species, tantalum in this example, will contaminate and degrade the shield to the extent it becomes inoperative. The contaminated and degraded shield must then be replaced with a new one. The spent ceramic shield can be refurbished to reduce maintenance costs of the deposition equipment. Typically, the spent ceramic ring is treated by first removing the metallic layer(s) from the ceramic substrate. The old metallic layer(s) are typically removed by immersing the deposition ring in a heated solution of potassium hydroxide. The potassium hydroxide solution dissolves the aluminum layer, thereby undercutting the tantalum layer. Although the potassium hydroxide solution is useful for removing the old metallic layer(s), it also has a tendency to damage the surface of the ceramic substrate, thereby weakening the bonding of the initial metallic layer to the ceramic substrate resulting in undesirable delamination and flaking.
Accordingly, there is a need to develop a method for removing a metallic layer(s) from the surface of a ceramic substrate without damaging the ceramic substrate to ensure that no delamination of the re-applied metallic layer will occur. There is a further need to develop a method for removing a metallic layer from the surface of a ceramic substrate while enhancing the surface of the ceramic substrate for subsequent re-coating.